Constructing Hierarchical Tectorum‐like α‐Fe2O3/PPy Nanoarrays on Carbon Cloth for Solid‐State Asymmetric Supercapacitors

The design of complex heterostructured electrode materials that deliver superior electrochemical performances to their individual counterparts has stimulated intensive research on configuring supercapacitors with high energy and power densities. Herein we fabricate hierarchical tectorum‐like α‐Fe₂O₃/polypyrrole (PPy) nanoarrays (T‐Fe₂O₃/PPy NAs). The 3D, and interconnected T‐Fe₂O₃/PPy NAs are successfully grown on conductive carbon cloth through an easy self‐sacrificing template and in situ vapor‐phase polymerization route under mild conditions. The electrode made of the T‐Fe₂O₃/PPy NAs exhibits a high areal capacitance of 382.4 mF cm⁻² at a current density of 0.5 mA cm⁻² and excellent reversibility. The solid‐state asymmetric supercapacitor consisting of T‐Fe₂O₃/PPy NAs and MnO₂ electrodes achieves a high energy density of 0.22 mWh cm⁻³ at a power density of 165.6 mW cm⁻³.     

Synthesis and characterization of a novel polyurethane/polypyrrole‐p‐toluenesulfonate (PU/PPy‐pTS) electroactive nanofibrous bending actuator

Electroactive actuators based on conductive polymers currently have attracted a great deal of attention. In this study, a nanofibrous structure of polypyrrole (PPy) was used to fabricate an electroactive bending actuator. For this purpose, polyurethane/PPy (PU/PPy) nanofibrous bending actuator was fabricated through the combined use of electrospinning and in‐situ chemical polymerization. The response surface methodology (RSM) was considered to find the optimal electrospinning conditions for producing PU nanofibers with the minimum diameter. The in‐situ chemical polymerization method was then used to prepare a conductive layer of PPy on the surface of optimum electrospun nanofibers with p‐toluenesulfonate (pTS) as the dopant. The coated nanofibers were used in the fabrication of PU/PPy‐pTS nanofibrous bending actuator. The morphology and electrical, thermal, electrochemical, and electrochemomechanical properties of the fabricated actuator were investigated. By using optimum conditions of electrospinning, PU nanofibers were obtained with a diameter of 221 nm. The results showed that the produced PU/PPy‐pTS nanofibers enjoy good thermal stability and have an electrical conductivity of about 276.34 S/cm. The obtained cyclic voltammetric and dynamo‐voltammetric responses showed that the dominant mechanism of actuation in the fabricated PU/PPy‐pTS nanofibrous actuator is the exchange of perchlorate anions with a partial exchange of lithium cations in 1M lithium perchlorate electrolyte solution. The fabricated actuator was capable of undergoing 141° reversible angular displacement during a potential cycle. The results demonstrated that, given high porosity, large specific surface area, flexibility, and desirable electrical properties, PU/PPy nanofibrous electroactive actuator provides a lot of potential for developing artificial muscle applications.     

Preparation of NiAl double hydroxide@polypyrrole materials for high‐performance supercapacitors

A novel NiAl double hydroxide@polypyrrole (LDH@PPy) core–shell material was designed and fabricated by a facile in situ oxidative polymerization of pyrrole (Py) monomer. The microstructure and morphology of the LDH@PPy composites were determined by X‐ray diffractometer, Fourier transform infrared (FTIR), scanning electron microscopy/transmission electron microscopy, and thermogravimetric and differential thermal, revealing that the polypyrrole (PPy) was successfully coated onto the surface of the NiAl‐LDH (LDH) core and the loading amount of PPy impacted the thickness and the dispersion of the conductive PPy shell. The electrochemical performances of the LDH@PPy composites were also evaluated by cyclic voltammogram, electrochemical impedance spectroscopy, and galvanostatic charge–discharge measurements. The results indicated that the supercapacitor performances were attributed to the synergy of unique core–shell heterostructure and each individual component, where the LDH core provided the high‐energy storage capacity and the PPy shell with networks had high electronic conductivity. These shorted the ion diffusion pathway and made electrolyte ions more easily accessible for faradic reactions to enhance the electrochemical performance of the LDH@PPy composites. It was found that the LDH@PPy composite (LDH@PPy₇) fabricated at 7 mL?L^?1 of Py monomer feed exhibiting the best electrochemical performances with high specific capacitance of 437.5 F?g^?1 at 2 A?g^?1 and excellent capacitance retention of about 91% after 1000 cycles. The work provides a simple approach for designing organic–inorganic core–shell materials with potential application in supercapacitors. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1653–1662     

Observation of Charge Separation and Space‐Charge Region in Single‐Crystal P3HT/C60 Heterojunction Nanowires

We directly observed charge separation and a space‐charge region in an organic single‐crystal p–n heterojunction nanowire, by means of scanning photocurrent microscopy. The axial p–n heterojunction nanowire had a well‐defined planar junction, consisted of P3HT (p‐type) and C₆₀ (n‐type) single crystals and was fabricated by means of the recently developed inkjet‐assisted nanotransfer printing technique. The depletion region formed at the p–n junction was directly observed by exploring the spatial distribution of photogenerated carriers along the heterojunction nanowire under various applied bias voltages. Our study provides a facile approach toward the precise characterization of charge transport in organic heterojunction systems as well as the design of efficient nanoscale organic optoelectronic devices.     

Application of Al2O3 in the electrosynthesis of polypyrrole with fuzzy morphology—Microtentacle

Polypyrrole (PPy) thin films were electrochemically polymerized onto the electrode surface. In this study alumina was used as the template and PPy film was prepared by electrochemical polymerization using Al/Al₂O₃ as the working electrode. Surface morphology of PPy was investigated by scanning electron microscopy (SEM) and the results revealed that the application of the template resulted in PPy with fantastic surface morphology which was called microtentacle and the length of the tentacle could reach 15 µm. The morphology can evidently increase the roughness, thus the surface area of the electrode substrate, and provide an intimate contact with the surrounding brain tissue compared to the hard, stiff metal surface. Relationship between PPy morphology and electrochemical polymerization parameters, such as polymerization time, was investigated. The study provided a fundamental method to prepare a PPy‐modified electrode with high surface area. Potential application of the study is proposed. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis,characterization, and properties of monodispersed magnetite coated multi‐walled carbon nanotube/polypyrrole nanocomposites synthesized by in‐situ chemical oxidative polymerization

This study describes the preparation of a nanocomposites fabricated from monodispersed 4‐nm iron oxide (Fe₃O₄) coated on the surface of carboxylic acid containing multi‐walled carbon nanotube (c‐MWCNT) and polypyrrole (PPy) by in situ chemical oxidative polymerization. High‐resolution transmission electron microscopy images and X‐ray diffraction (XRD) data indicate that the resulting Fe₃O₄ nanoparticles synthesized using the thermal decomposition are close to spherical dots with a particle size about 4 ± 0.2 nm. The resulting nanoparticles were further mixed with c‐MWCNT in an aqueous solution containing with anionic surfactant sodium bis(2‐ethylhexyl) sulfosuccinate to form one‐dimensional Fe₃O₄ coated c‐MWCNT template for further preparation of nanocomposite. Structural and morphological analysis using field‐emission scanning electron microscopy, high‐resolution transmission electron microscopy, and XRD showed that the fabricated Fe₃O₄ coated c‐MWCNT/PPy nanocomposites are one‐dimensional core (Fe₃O₄ coated c‐MWCNT)‐shell (PPy) structures. The conductivities of these Fe₃O₄ coated c‐MWCNT/PPy nanocomposites are about four times higher than those of pure PPy matrix. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 727–733, 2008     

Patterned Growth of Vertically Aligned Polypyrrole Nanowire Arrays

A facile strategy for preparing vertically aligned polypyrrole (PPy) nanoarrays with precisely controlled density and quantity is presented. The method involves two steps: (1) the fabrication of the patterned substrate via electron beam lithography and (2) the controlled growth of PPy nanowires via electrochemical polymerization on the patterned substrate. The electrical property of a single PPy nanowire is investigated via in situ conducting probe atomic force microscopy.     

Electroconductive Hydrogels: Electrical and Electrochemical Properties of Polypyrrole‐Poly(HEMA) Composites

Composites of inherently conductive polypyrrole (PPy) within highly hydrophilic poly(2‐hydroxyethyl methacrylate)‐based hydrogels (p(HEMA)) have been fabricated and their electrochemical properties investigated. The electrochemical characteristics observed by cyclic voltammetry suggest less facile reduction of PPy within the composite hydrogel compared to electropolymerized PPy, as shown by the shift in the reduction peak potential from ?472 mV for electropolymerized polypyrrole to ?636 mV for the electroconductive composite gel. The network impedance magnitude for the electroconductive hydrogel remains quite low, ca. 100 Ω, even upon approach to DC, over all frequencies and at all offset potentials suggesting retained electronic (bipolaronic) conductivity within the composite. In contrast, sustained application of +0.7 V (vs. Ag/AgCl, 3 M Cl^?) for typically 100 min. (conditioning) to reduce the background amperometric current to <1.0 μA, resulted in complete loss of electroactivity. Nyquist plots suggest that sustained application of such a modest potential to the composite hydrogel results in impedance characteristics that resembles p(HEMA) without evidence of the conducting polymer component. PPy composite gels supported a larger ferrocene monocarboxylate diffusivity (D_appt=7.97×10^?5 cm² s^?1) compared to electropolymerized PPy (D_appt=5.56×10^?5 cm² s^?1), however a marked reduction in diffusivity (D_appt=1.01×10^?5 cm² s^?1) was observed with the conditioned hydrogel composite. Cyclic voltammograms in buffer containing H₂O₂ showed an absence of redox peaks for electrodes coated with PPy‐containing membranes, suggesting possible chemical oxidation of polypyrrole by the oxidant     

Fabrication of Electrically Conducting Polypyrrole‐Poly(ethylene oxide) Composite Nanofibers

Summary: Electrically conducting polypyrrole‐poly(ethylene oxide) (PPy‐PEO) composite nanofibers are fabricated via a two‐step process. First, FeCl₃‐containing PEO nanofibers are produced by electrospinning. Second, the PEO‐FeCl₃ electrospun fibers are exposed to pyrrole vapor for the synthesis of polypyrrole. The vapor phase polymerization occurs through the diffusion of pyrrole monomer into the nanofibers. The collected non‐woven fiber mat is composed of 96 ± 30 nm diameter PPy‐PEO nanofibers. FT‐IR, XPS, and conductivity measurements confirm polypyrrole synthesis in the nanofiber.

An SEM image of the PPy‐PEO composite nanofibers. The scale bar in the image is 500 nm.     

Electrochemical Behavior of Polypyrrole‐modified SnS2 for Use as Anode Material in Lithium‐Ion Batteries

SnS₂/polypyrrole (PPy) composites were successfully synthesized by PPy modification of SnS₂ via a simple and effective solvothermal and chemical method. The microstructure, morphology, electrical conductivity, PPy content, and electrochemical properties of these materials were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), four‐point probe technique, thermogavimetry (TG), and constant‐current charge/discharge tests, respectively. The results demonstrate that PPy is tightly coated on the 3D flower‐like SnS₂ and that the conductivity of SnS₂ /PPy composites can be greatly improved by the PPy modification. The electrochemical results indicate that PPy is not involved in the electrode reaction, but it can dramatically improve the reversible capacity and cyclic performance. The recharge capacity retention after 30 cycles remained at 523 mAh/g, which is significantly higher than that of SnS₂ without modification by PPy. The better cycling performance compared to SnS₂ nanoparticles should be due to the 3D nano‐flower‐like SnS₂ particles and the modification of SnS₂ by PPy.     

A Highly Elastic and Reversibly Stretchable All‐Polymer Supercapacitor

Multiple stretchability has never been demonstrated as supercapacitors because the hydrogel used cannot fully recover after being heavily deformed. Now, a highly reversibly stretchable all‐polymer supercapacitor was fabricated using a developed double network hydrogel (DN hydrogel) as electrolyte and pure polypyrrole (PPy) as electrode. The DN hydrogel provides excellent mechanical properties, which can be stretched up to 500 % many times and then restore almost 100 % of the original length. To fabricate the fully recoverable stretchable supercapacitor, we annealed a free‐standing pure conducting polymer film as electrode so that the electrodes induced retardance is minimized. The as‐fabricated DN hydrogel/pure conducting polymer supercapacitors can be perfectly recovered from 100 % strain with almost no residual deformation left and the electrochemical performance can be maintained even after 1000 stretches (but not bending).     

Preparation of a NiAl‐Oxide@Polypyrrole Composite for High‐Performance Supercapacitors

A core‐shell NiAlO@polypyrrole composite (NiAlO@PPy) with a 3D “sand rose”‐like morphology was prepared via a facile in situ oxidative polymerization of pyrrole monomer, where the role of PPy coating thickness was investigated for high‐performance supercapacitors. Microstructure analyses indicated that the PPy was successfully coated onto the NiAlO surface to form a core‐shell structure. The NiAlO@PPy exhibited a better electrochemical performance than pure NiAlO, and the moderate thickness of the PPy shell layer was beneficial for expediting the electron transfer in the redox reaction. It was found that the NiAlO@PPy₅ prepared at 5.0 mL L^?1 addition amount of pyrrole monomer demonstrated the best electrochemical performance with a high specific capacitance of 883.2 F g^?1 at a current density of 1 A g^?1 and excellent capacitance retention of 91.82 % of its initial capacitance after 1000 cycles at 3 A g^?1. The outstanding electrochemical performance of NiAlO@PPy₅ were due to the synergistic effect of NiAlO and PPy, where the uniform network‐like PPy shell with the optimal thickness made electrolyte ions more easily accessible for faradic reactions. This work provided a simple approach for designing organic–inorganic core‐shell materials as high‐performance electrode materials for electrochemical supercapacitors.     

A Self‐Healing Integrated All‐in‐One Zinc‐Ion Battery

The self‐healing of zinc‐ion batteries (ZIBs) will not only significantly improve the durability and extend the lifetime of devices, but also decrease electronic waste and economic cost. A poly(vinyl alcohol)/zinc trifluoromethanesulfonate (PVA/Zn(CF₃SO₃)₂) hydrogel electrolyte was fabricated by a facile freeze/thaw strategy. PVA/Zn(CF₃SO₃)₂ hydrogels possess excellent ionic conductivity and stable electrochemical performance. Such hydrogel electrolytes can autonomously self‐heal by hydrogen bonding without any external stimulus. All‐in‐one integrated ZIBs can be assembled by incorporating the cathode, separator, and anode into hydrogel matrix since the fabrication of PVA/Zn(CF₃SO₃)₂ hydrogel is a process of converting the liquid to quasi‐solid state. The ZIBs show an outstanding self‐healing and can recover electrochemical performance completely even after several cutting/healing cycles.     

Fabrication and Properties of Conducting Polypyrrole/SWNT‐PABS Composite Films and Nanotubes

We report the electropolymerization and characterization of polypyrrole films doped with poly(m‐aminobenzene sulfonic acid (PABS) functionalized single‐walled nanotubes (SWNT) (PPy/SWNT‐PABS). The negatively charged water‐soluble SWNT‐PABS served as anionic dopant during the electropolymerization to synthesize PPy/SWNT‐PABS composite films. The synthetic, morphological and electrical properties of PPy/SWNT‐PABS films and chloride doped polypyrrole (PPy/Cl) films were compared. Characterization was performed by cyclic voltammetry, atomic force microscopy (AFM), scanning electron microscopy (SEM) and Raman spectroscopy. SEM and AFM images revealed that the incorporation of SWNT‐PABS significantly altered the morphology of the PPy. Cyclic voltammetry showed improved electrochemical properties of PPy/SWNT‐PABS films as compared to PPy/Cl films. Raman Spectroscopy confirmed the presence of SWNT‐PABS within composite films. Field effect transistor (FET) and electrical characterization studies show that the incorporation of the SWNT‐PABS increased the electronic performance of PPy/SWNT‐PABS films when compared to PPy/Cl films. Finally, we fabricated PPy/SWNT‐PABS nanotubes which may lead to potential applications to sensors and other electronic devices.     

One‐pot Electro‐polymerized SDPAS/PPy/CNTs Modified Electrode for Selective Detection of Dopamine

To improve the performance of dopamine (DA) detection in the presence of ascorbic acid (AA) and uric acid (UA), sodium diphenylamine sulfonate/polypyrrole/multi‐walled carbon nanotubes (SDPAS/PPy/CNTs) film was fabricated on the surface of gold electrode through one‐pot polymerization initiated by electrochemical oxidation. SDPAS were covalently embedded into the backbone of PPy to endow the resultant film with numerous negative‐charged terminals, resulting in selective pre‐adsorption of protonated DA⁺ on the electrode and switching the following anodic reaction to be an adsorption‐controlled process. The detection of DA in the presence of AA and UA by square wave voltammetry method showed an outstanding repeatability with the relative standard deviation of 0.45 %. A good linear relationship was observed between the oxidative peak current and the concentration of DA in the range of 0.827–104 μM (R²=0.993), and the limit of detection (LOD) was calculated to be 0.105 μM (S/N=3).     

Preparation and characterization of conducting poly(acryloyl chloride)‐g‐ polypyrrole copolymer

The electroactive copolymer of poly(acryloyl chloride) (PAC) and polypyrrole (PPy) can be synthesized by electrochemical polymerization using a polymer precursor which contains a pyrrole moiety in its side chain. Poly(acryloyl pyrrole) (PAP) was synthesized chemically with acryloyl chloride and potassium pyrrole salt and characterized using FT‐IR and ¹H‐NMR spectroscopy. PAP dissolved in dimethyl formamide (DMF), was spin‐coated on a platinum electrode and polymerized electrochemically in the electrolytic mixture solution consisting of acetonitrile, 0.1 M pyrrole, and 0.1 M lithium perchlorate. Constant potential electrolysis showed that pyrrole groups in the precursor were oxidized to form PPy, that is, they acted as grafting centers at which the PPy grew. Scanning electron microscopy (SEM) results and conductivity measurements supported the formation of the graft copolymer. The morphological feature of PAC‐g‐PPy copolymer films showed homogeneous structure, but that of PAC/PPy composite films showed irregular structure. The maximum conductivity of the final products was about 1 S/cm. Copyright © 2002 John Wiley & Sons, Ltd.     

Organic–inorganic polypyrrole‐surface modified SiO2 hybrid nanocomposites: a facile and green synthetic approach

Organic–inorganic hybrid nanocomposites composed of conductive polypyrrole (PPy) and surface modified silica (SiO₂) were successfully prepared through an in situ chemical oxidative polymerization in supercritical carbon dioxide (scCO₂). SiO₂ nanoparticles were surface modified using 3‐methacryloxypropyltrimethoxysilane (MPTMS) in order to disperse well in the medium. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that the SiO₂ nanoparticles were encapsulated into the polymer. UV‐visible spectra of the diluted colloidal dispersions of PPy/SiO₂ hybrid nanocomposites were similar to those of PPy system. Fourier transform infrared spectroscopy (FT‐IR) suggested the strong interaction between PPy and SiO₂. Surface characterizations of nanocomposites were described by X‐ray photoelectron spectroscopy (XPS). The nanocomposites synthesized in scCO₂ have been shown to possess higher electrical conductivity and thermal stability. Copyright © 2009 John Wiley & Sons, Ltd.     

Magnetic ionic liquid‐assisted synthesis of polypyrrole/AgCl nanocomposites

The synthesis of polypyrrole (PPy)/AgCl nanocomposites with their size ranging around 70–100 nm are achieved by using magnetic ionic liquid as the oxidant in the interface polymerization system. The interface polymerization leads to the formation of uniform and unaggregated nanocomposites with a relatively narrow size distribution confined to submicrometer‐sized domains. The morphology and structure of the nanocomposites are characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and X‐ray diffraction (XRD). The potential application of PPy/AgCl nanocomposites as a H₂O₂ biosensor is also reported. Copyright © 2010 John Wiley & Sons, Ltd. Erratum: Magnetic ionic liquid‐assisted synthesis of polypyrrole/AgCl nanocomposites     

Hydrogel Membrane Improves Batch‐to‐Batch Reproducibility of an Enzymatic Glucose Biosensor

A permselective membrane is a critical component that defines the linear detection limits, the sensitivity, and thus the ultimate efficacy of an enzymatic biosensor. Although membranes like epoxy‐polyurethane (epoxy‐PU) and Nafion are widely used and provide the desired glucose detection limits of 2 to 30 mM, both the within batch and batch‐to‐batch variability of sensors that use these materials is a concern. The hypothesis for this study was that a crosslinked hydrogel would have a sufficiently uniform porosity and hydrophilicity to address the variability in sensor sensitivity. The hydrogel was prepared by crosslinking di‐hydroxyethyl methacrylate, hydroxyethyl methacrylate and N‐vinyl pyrrolidone with 2.5 mol% ethylene glycol dimethacrylate using water soluble initiators – ammonium persulfate and sodium metabisulfite under a nitrogen atmosphere. The hydrogel was applied to the sensor by dip coating during polymerisation. Electrochemical measurements revealed that the response characteristics of sensors coated with this membrane are highly consistent. Scanning electrochemical microscopy (SECM) was used to spatially resolve glucose diffusion through the membrane by measuring the consequent H₂O₂ release and compared with an epoxy‐PU membrane. Hydrogen peroxide measurements using SECM revealed that the epoxy‐PU membranes had uneven lateral diffusion profiles compared to the uniform profile of the hydrogel membranes. The uneven diffusion profiles of epoxy‐PU membranes are attributed to a fabrication method that results in uneven membrane properties, while the uniform diffusion profiles of the hydrogel membranes are primarily dictated by their uniform pore size.     

Synthesis of millimeter‐sized hydrogel beads by inverse Pickering polymerization using starch‐based nanoparticles as emulsifier

The preparation of millimeter‐sized poly(acrylamide‐co‐acrylic acid) hydrogel beads via inverse Pickering emulsion polymerization using starch‐based nanoparticles (SNPs) as stabilizers is reported. Amphiphilic starch is fabricated by the introduction of butyl glycidyl ether groups and palmitate groups, and the hydrophobically modified SNPs are fabricated by a nanoprecipitation process. The obtained SNPs could adsorb at oil‐water interfaces to stabilize an inverse Pickering emulsion, and the effects of oil/water volume fraction ratio and SNP concentration on emulsions are comprehensively studied. Poly(acrylamide‐co‐acrylic acid) hydrogel beads with a size of approximately 1 mm are obtained by inverse Pickering emulsion polymerization stabilized by SNPs. The morphology and structure of hydrogel beads are extensively investigated, which confirms that SNPs locate on the surface of hydrogel beads and act as emulsifiers and network structures present inside the beads. Polymerization is also detected to investigate the potential formation mechanism of hydrogel beads. The pH‐responsive property of hydrogel beads and its potential application for drug delivery are also explored.